On July 30, 2016, Alfred “Skip” Nichols was piloting a hot air balloon with 15 sight-seeing passengers when the hot air balloon struck power lines and crashed into the ground, killing all 16 people on board.

After the crash, news surfaced that Nichols had four previous drunken driving convictions in Missouri and spent time in prison for drugs, law enforcement officials said.

In addition, Nichols’ driver’s license had been suspended twice and he was sued over a 2009 balloon landing that a passenger said left her injured, documents show.

Nichols didn’t have to tell the FAA about those problems because oversight for balloon pilots is not as stringent as for airline or helicopter pilots, the National Transportation Safety Board said. They are expected to self-report any drug or alcohol driving offenses within 60 days, the FAA says.

Unlike pilots for other aircraft, balloon pilots are not required to obtain an FAA medical certificate to fly, NTSB member Robert Sumwalt said.

After the crash, the NTSB confirmed that they would conduct a routine toxicology test to confirm if Nichols was under the influence of any drugs or alcohol at the time of the horrific crash.

“The ultimate goal of this investigation is to learn from this tragedy so that we can keep it from happening again,” Sumwalt said in opening remarks at Friday’s hearing.

Through the NTSB’s investigation, officials found Nichols was taking 13 prescription medicines for his multiple medical problems including type II diabetes, depression and chronic pain from fibromyalgia.